System Description

Fuel Delivery System:

The fuel system consists of three major subsystems; a fuel storage system, a Feedback Carburetor with its supporting control system, and a fuel delivery and return system.

FUEL STORAGE
The fuel storage system consists of a fuel tank, a fill spout and filler cap. The filler cap is of a pressure vacuum design to eliminate fuel vapors escaping to the atmosphere. The fill spout contains a restrictor to prevent the addition of leaded fuel to the tank.

FEEDBACK CARBURETOR SYSTEM
The carburetor includes special design features to obtain optimum air/fuel mixtures during all engine operating modes. Fuel metering is accomplished through the use of two solenoid operated valves (Feedback and Slow cut solenoids) which add or reduce fuel to the engine as necessary. The activation of the valves is controlled by the length of time current is supplied to the solenoids. The solenoid valves operate at a fixed frequency. By varying the amount of time the solenoids are energized during each cycle (duty cycle), the air/fuel mixture delivered to the engine can be precisely controlled. The duty cycle to the solenoids is controlled by the electronic control unit (ECU) in response to signals received from various sensors. The primary difference between the California and Federal systems is in the vacuum sources used to control the high altitude compensation system.

FUEL DELIVERY AND RETURN
The fuel delivery components consist of fuel supply and delivery lines, a mechanical fuel pump and a fuel filter assembly. The Fuel return portion of the fuel system consists of lines and couplings and includes the vapor recovery system. The function of the return line is to recover excess fuel vented from the fuel pump check valve (to relieve excess pump pressure) and return it through the accelerator pump housing, to the fuel tank. The return line is a low pressure part of the fuel system.
The function of the vapor recovery lines are to provide a route for the recovery of fuel vapors (both from the fuel tank and the float bowl) either for storage in the charcoal canister, or for evacuation through the purge control system. Additionally contained in the vapor recovery system are two components, an overfill limiter and a fuel check valve. The overfill limiter is mounted between the fuel tank the the fuel check valve, and limits the amount of pressure or vacuum bled to the fuel tank, through the check valve. The fuel check valve acts as a rollover valve, and prevents liquid fuel from reaching the evaporative canister in the event of a vehicle rollover.